The purpose of the proposed research is to assess the ability of children with a limited functional articulation disorder - the substitution of (t) for (s) - to label the speech sounds they articulate correctly and incorrectly. Previous research using natural speech signals in discrimination tasks with heterogeneous groups of articulation disordered children has not led to a consistent picture of the relationship between deviant articulation and phonetic perception. To gain a purchase on that relationship we propose using synthetic speech signals in identification tasks with a homogeneous group of articulation disordered children. The feasibility of this approach has been demonstrated in a pilot experiment in which it was found that children who substitute (t) for (s) in production did not label normally signals from along a (s) to (t) continuum, i.e., a duration of friction continuum, but did label normally signals which they did produce contrastively, i.e., from along a voice onset time continuum. We now propose (1) to replicate and extend the pilot experiment using more subjects and more appropriate range of synthetic stimuli; (2) to discover how much friction duration is necessary for "s-less" children to label a signal as (s); (3) to assess the variability of (s)-labeling performance in a large sample of "s-less" children and (4) to follow the changes in (s)-labeling performance during speech therapy. In general, then, the proposal examines differences in phonetic processing between normal children and children with a specific function articulation disorder.